Abstract: Because the modal strain energy is sensitive to structural local deformation, in the assembly structure which represented by bolt connection structure, the influence of load force change on contact stiffness and inherent characteristics can adopt the method of modal strain energy. Contact stiffness identification method is proposed based on this method which can improve the accuracy of rough surface contact stiffness identification. Taking the bolt-connected T-block experimental structure as an example, the first 3 natural frequencies under different load forces of bolt are tested, and then rough surface contact characteristics are equalized by using thin layer elements method. Considering the modal strain energy weights of the structure, the contact stiffness identified and identification error is discussed. The results show that the modal strain energy weights of each order may show different trends with the change of contact stiffness or bolt load force, which leads to great differences between the results of contact stiffness identification based on single mode. The results of contact stiffness identification based on modal strain energy which considers modal strain energy weights of each order reflect the overall change trend of natural frequencies. With the increase of the load force of the bolt, contact stiffness generally increase, but the identification error generally decrease. Based on the modal strain energy, the contract stiffness identification method is proposed, and the coupling mechanism of pre-tightening force variable, rough surface contact stiffness and modal natural frequency is established, which provides an accurate identification method for rough surface contact stiffness modeling.

Key words: contact stiffness, thin layer element method, stiffness identification, contact mechanics, bolted connection structure